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to display a different component with each click (using hooks)

I want to display a different component with each button click.
I'm sure the syntax is wrong, can anyone help me? The browser doesn't load
I would love an explanation of where I went wrong
One component (instead of HomePage) should display on the App component after clicking the button. Help me to understand the right method.
Thanks!
App.js
import React, {useState} from 'react';
import './App.css';
import Addroom from './components/Addroom.js'
import HomePage from './components/HomePage.js'
function App() {
const [flag, setFlage] = useState(false);
return (
<div className="App">
<h1>My Smart House</h1>
<button onClick={()=>{setFlage({flag:true})}}>Addroom</button>
<button onClick={()=>{setFlage({flag:false})}}>HomePage</button>
{setState({flag}) && (
<div><Addroom index={i}/></div>
)}
{!setState({flag}) && (
<div><HomePage index={i}/></div>
)}
</div>
)
}
export default App;
HomePage
import React from 'react'
export default function HomePage() {
return (
<div>
HomePage
</div>
)
}
Addroom
import React from 'react'
export default function Addroom() {
return (
<div>
Addroom
</div>
)
}

I didn't test it but as i can see it should be something like this:
<button onClick={()=>setFlage(true)}>Addroom</button>
<button onClick={()=>setFlage(false)}>HomePage</button>
{flag && (
<div><Addroom index={i}/></div>
)}
{!flag && (
<div><HomePage index={i}/></div>
)}
You need to call setFlage function with argument of Boolean saying true or false and it changes the flag variable that you want to read.

Try the following.
function App() {
const [flag, setFlage] = useState(false);
return (
<div className="App">
<h1>My Smart House</h1>
<button
onClick={() => {
setFlage(true);
}}
>
Addroom
</button>
<button
onClick={() => {
setFlage(false );
}}
>
HomePage
</button>
{flag ? <Addroom /> : <HomePage /> }
</div>
);
}

You are missing render methods and also you should use setState for reactive rendering.( when you use state variables and once value changed render method will rebuild output so this will load your conditinal component.
https://jsfiddle.net/khajaamin/f8hL3ugx/21/
--- HTML
class Home extends React.Component {
constructor(props) {
super(props);
}
render() {
return <div> In Home</div>;
}
}
class Contact extends React.Component {
constructor(props) {
super(props);
}
render() {
return <div> In Contact</div>;
}
}
class TodoApp extends React.Component {
constructor(props) {
super(props);
this.state = {
flag: false,
};
}
handleClick() {
this.setState((state) => ({
flag: !state.flag,
}));
console.log("hi", this.state.flag);
}
getSelectedComp() {
if (this.state.flag) {
return <Home></Home>;
}
return <Contact></Contact>;
}
render() {
console.log("refreshed");
return (
<div>
<h1>
Click On button to see Home component loading and reclick to load back
Contact component
</h1
<button onClick={() => this.handleClick()}>Switch Component</button>
{this.getSelectedComp()}
</div>
);
}
}
ReactDOM.render(<TodoApp />, document.querySelector("#app"));

react setState() is not working on first click but works fine on 2nd,3rd......clicks

setState() doesn't work on first click ! the state value gets updated only on second , third ....clicks. i used proper contexts and imports to handle the states!
I'll quickly summarize what im doing top nav bar has two buttons , home and cart.
Side nav bar has three hero buttons, on click renders the respective hero store which has tshirts , socks and shoes with + and - buttons to increase or decrease the quantity.
on each click the value of span that displays the quantity increases correctly but the cart buttons shows the quantity excluding the first clicks. Like when i increment the tshirts value to 1 , the cart button doesn't show any value ,as i increment the tshirts value to 2 the cart button shows 1
cartButton uses the state CartValue
tshirts,socks,shoes use the state HeroGoods
(live demo) click here to see the what im talking about
i'm not sure if im allowed to post all the components and external links like github here. but anyways if you guys cant see where i went wrong from the code below , here's link to the github repo
import React , {useState,useEffect}from 'react';
import Navmenu from './Navmenu'
import SideNav from './SideNav'
import ActionDiv from './ActionDiv'
import ActionHeroStore from './ActionHeroStore'
import ActionCart from './ActionCart'
import '../css/main.css'
export const HeroContext=React.createContext()
const emptyGood={
tshirts:0,
shoes:0,
socks:0,
}
const emptyCart={
batman:{
tshirts:0,
shoes:0,
socks:0,
},
superman:{
tshirts:0,
shoes:0,
socks:0,
},
greenlantern:{
tshirts:0,
shoes:0,
socks:0,
},
}
function empty()
{
return null
}
function App() {
const [hero,setHero]=useState(null)
const [cartValue,setCartValue]=useState(emptyCart)
const [batmanGoods,setBatmanGoods]=useState(emptyGood)
const [supermanGoods,setSupermanGoods]=useState(emptyGood)
const [greenLanternGoods,setGreenLanternGoods]=useState(emptyGood)
const [showCart,setShowCart]=useState(false)
function handleUpdateGoods(hero,obj){
hero=='batman'?
setBatmanGoods(prevState=>{
return {...prevState,...obj}
}):
hero=='superman'?
setSupermanGoods(prevState=>{
return {...prevState,...obj}
}):
hero=='greenlantern'?
setGreenLanternGoods(prevState=>{
return {...prevState,...obj}
}):
empty()
}
function handleHeroSelect(name){
setHero(prevState=>prevState=name)
}
function handleCartValue(value)
{
setCartValue(value)
}
function handleShowCart(status)
{
setShowCart(status)
}
function giveHeroGoods(hero,element)
{
return (
hero=='batman'?batmanGoods[element]:
hero=='superman'?supermanGoods[element]:
hero=='greenlantern'?greenLanternGoods[element]:empty()
)
}
function handleUpdateCart(name){
name=='batman'?
setCartValue(prevState=>{
return {...prevState,batman:{...batmanGoods}}
}):
name=='superman'?
setCartValue(prevState=>{
return {...prevState,superman:{...supermanGoods}}
}):
name=='greenlantern'?
setCartValue(prevState=>{
return {...prevState,greenlantern:{...greenLanternGoods}}
}):
empty()
}
const heroContextValue={
handleHeroSelect,
handleCartValue,
handleUpdateGoods,
giveHeroGoods,
handleUpdateCart,
handleShowCart
}
return (
<>
<HeroContext.Provider value={heroContextValue}>
<Navmenu cartValue={cartValue}/>
<div className="mainContent">
<SideNav cartValue={cartValue}/>
{hero==null && !showCart &&<ActionDiv/>}
{hero!==null && !showCart && <ActionHeroStore hero={hero}/>}
{showCart && <ActionCart cartValue={cartValue}/>}
</div>
</HeroContext.Provider>
</>
)
}
export default App;
import React ,{useContext} from 'react'
import {HeroContext} from './App'
export default function Navmenu(props) {
const {cartValue}=props
const {handleHeroSelect,handleShowCart}=useContext(HeroContext)
function giveGoodsSum(obj)
{
return obj.tshirts+obj.socks+obj.shoes
}
function giveCartValue(cartValue){
let sum=0
for(let key in cartValue)
{
sum=sum+giveGoodsSum(cartValue[key])
}
return(
sum!==0?sum:null
)
}
return (
<div
className="navMenu"
>
<button
className="homeButton"
onClick={()=>{
handleHeroSelect(null)
handleShowCart(false)
}}
>
Home
</button>
<button
className="cartButton"
onClick={()=>{
handleHeroSelect(null)
handleShowCart(true)
}}
>
cart
<span
>
{giveCartValue(cartValue)}
</span>
</button>
</div>
)
}
import React ,{useContext} from 'react'
import {HeroContext} from './App'
export default function SideNav() {
const {handleHeroSelect}=useContext(HeroContext)
return (
<div className="sideNav">
<div
className="batman"
onClick={()=>handleHeroSelect('batman')}
/>
<div
className="superman"
onClick={()=>handleHeroSelect('superman')}
/>
<div
className="greenlantern"
onClick={()=>handleHeroSelect('greenlantern')}
/>
</div>
)
}
import React from 'react'
import ActionHeroStoreGoods from './ActionHeroStoreGoods'
export default function ActionHeroStore(props) {
const {hero}=props
return (
<div className={`actionHeroStore ${hero}div`}>
<h3>{hero}</h3>
<div className="actionHeroStore_goods">
<ActionHeroStoreGoods hero={hero}/>
</div>
</div>
)
}
import React, { Fragment,useContext } from 'react'
import {HeroContext} from './App'
export default function ActionHeroStoreGoods({hero}) {
const {giveHeroGoods,
handleUpdateGoods,
handleUpdateCart
}=useContext(HeroContext)
const goods=['tshirts','shoes','socks'];
const goodsElement=goods.map((element,index) => {
return <Fragment key={index}>
<div className="soloGood">
<span>{element}</span>
<button
onClick={
()=>decrement(hero,element)
}>-</button >
<span>{giveHeroGoods(hero,element)}</span>
<button onClick={
()=>{
increment(hero,element)
handleUpdateCart(hero)
}
}>+</button>
</div>
</Fragment>
})
function increment(hero,element){
let updateObj={};
updateObj[element]=giveHeroGoods(hero,element)+1
handleUpdateGoods(hero,updateObj)
}
function decrement(hero,element){
if(giveHeroGoods(hero,element)>0)
{
let updateObj={};
updateObj[element]=giveHeroGoods(hero,element)-1
handleUpdateGoods(hero,updateObj)
}
}
return (
<>
{goodsElement}
</>
)
}

The problem is not in setState. The problem in the code. handleUpdateCart() function is called before the *Goods states are changed. So It works with old data. If you will add in the your 'App.js' file the following fragment:
...
...
function giveHeroGoods(hero,element)
{
return (
hero=='batman'?batmanGoods[element]:
hero=='superman'?supermanGoods[element]:
hero=='greenlantern'?greenLanternGoods[element]:empty()
)
}
// FROM HERE
React.useEffect(() => {
handleUpdateCart('batman');
}, [
batmanGoods
]);
React.useEffect(() => {
handleUpdateCart('superman');
}, [
supermanGoods
]);
React.useEffect(() => {
handleUpdateCart('greenlantern');
}, [
greenLanternGoods
]);
// TILL HERE
function handleUpdateCart(name){
...
...

Conditional rendering based on user input

I've just started learning React and am struggling with conditional rendering. I want to render components based on form input but i'm not sure what needs to be done or where it needs to be executed.
I have imported my Form component which has the input I want to use and have another component like this:
import React, {Component} from 'react';
import Form from './Form';
import CardOne from './CardOne';
import CardTwo from './CardTwo';
import CardThree from './CardThree';
export default class CardContainer extends Component {
render(){
return (
<div>
<CardOne />
<CardTwo />
<CardThree />
</div>
)
}
}
I basically want to be able to show certain Cards if the value of the input is greater than X when the form is submitted, but I don't know how to target an imported component.
This is my Form component:
export default class Form extends Component {
state = {
number: ''
};
change = (e) => {
this.setState({
[e.target.name]: e.target.value
});
};
onSubmit = e => {
e.preventDefault();
this.props.onSubmit(this.state);
this.setState({
number: ''
})
};
render(){
return (
<form>
<label>Number</label>
<input
type="number"
name="number"
placeholder="Number"
value={this.state.number}
onChange={e => this.change(e)} />
<button onClick={e => this.onSubmit(e)}>Submit</button>
</form>
)
}
}
Any help will be massively appreciated!

I have redesigned your Form component , Below is my code. . Let me know if u faced any issues on that .
import React, { Component } from 'react';
import CardOne from './CardOne';
import CardTwo from './CardTwo';
import CardThree from './CardThree';
export default class Form extends Component {
state = {
number: '',
showOne:true,
showTwo:false,
showThree:false,
userInputValue:''
};
change = (e) => {
this.setState({
userInputValue: e.target.value
});
};
onSubmit = e => {
e.preventDefault();
this.props.onSubmit(this.state);
if (this.state.userInputValue > 10 && this.state.userInputValue <20 ){
this.setState({
showTwo: true,
})
}
if (this.state.userInputValue > 20 && this.state.userInputValue < 30) {
this.setState({
showThree: true,
})
}
};
render() {
return (
<div>
<form>
<label>Number</label>
<input
type="number"
name="number"
placeholder="Number"
value={this.state.userInputValue}
onChange={e => this.change(e)} />
<button onClick={e => this.onSubmit(e)}>Submit</button>
</form>
<div>
{this.state.showOne ?
<CardOne />
:
<div></div>
}
{this.state.showTwo ?
<CardTwo />
:
<div></div>
}
{this.state.showThree ?
<CardThree />
:
<div></div>
}
</div>
</div>
)
}
}
// What i wrote above is your base functionality . You reedit the condition depends on ur requirement .

This is what I came up with following your logic of card rendering. I did not change Form coponent but rather worked on the Container
export default class CardContainer extends Component {
constructor(props) {
super(props);
state = {
number: 0,
}
this.onFormSubmit = this.onFormSubmit.bind(this);
}
onFormSubmit=(number)=>{
this.setState({ number: number });
}
render(){
let i=Math.floor(this.state.number/10)
return (
<div>
<Form onSubmit={() => this.onFormSubmit(number)}
[<CardOne />, <CardTwo />, <CardThree/>].slice(0,i).map(card =>
{card}
)
</div>
)
}
}

I would use render prop for this kind of problem. You can research more about render props but basically your CardContainer component will not render those cards component statically as it is. It will return props.children instead.
And then you will have a function (i.e function TestX) that will have a conditional to check what the value of X is. This is the function that will return either , , based on what X is. The function TestX will receive props from CardContainer, including the value of X that is read from the state.
So I will just use CardContainer component with as its child.

React.js targeting a single element with a shared onClick function

I am new to both coding as well as React.js, so any assistance in learning what I am doing incorrectly is greatly appreciated! I am creating multiple cards on a page with riddles where the answer is hidden via css. I am using an onClick function ("toggleAnswer") to toggle the state of each answer to change the className so that the answer will either be visible or hidden. Currently, the onClick event is changing the state for all the answers. I realize this is because my code is not targeting a particular element, but I am unsure how this can be done. How can this be achieved? My code is currently like this:
// RiddlesPage where toggleAnswer function is defined
class RiddlesPage extends Component {
constructor(props) {
super(props);
this.state = {
questionData: [],
isHidden: true
};
this.getPageData = this.getPageData.bind(this);
this.toggleAnswer = this.toggleAnswer.bind(this);
}
getPageData() {
console.log("we hit getPageData function starting --");
helpers.getRiddlesPage().then(data => {
console.log("this is the result", data);
this.setState({
questionData: data[0].questionData,
});
});
}
toggleAnswer(e) {
this.setState({ isHidden: !this.state.isHidden });
}
componentWillMount() {
this.getPageData();
}
render() {
const answerClass = this.state.isHidden ? "answer-hide" : "answer";
return (
<div>
<Riddles>
{this.state.questionData.map((data, index) => {
return (
<RiddlesItem
key={index}
id={index}
question={data.question}
answer={data.answer}
button={data.buttonURL}
answerClass={answerClass}
onClick={this.toggleAnswer}
/>
);
})}
</Riddles>
</div>
);
}
}
export default RiddlesPage;
// Riddles Component
import React from "react";
import "./riddles.css";
const Riddles = props => (
<div id="riddles-row">
<div className="container">
<div className="row">
<div className="col-12">
<div>{props.children}</div>
</div>
</div>
</div>
</div>
);
export default Riddles;
// RiddlesItem Component where onClick function is set as a prop
import React from "react";
import "./riddles.css";
const RiddlesItem = props => (
<div>
<div className="card-body">
<p id="question">{props.question}</p>
<img
className="img-fluid"
id={props.id}
src={props.button}
onClick={props.onClick}
alt="answer button"
/>
<p className={props.answerClass}> {props.answer} </p>
</div>
</div>
);
export default RiddlesItem;

You'd have to keep track of each answer that has been shown in state (in an array or something).
First
Send the index of the answer up in the onclick function. In that function, check if it exists in the "shownAnswers" array and either add or remove it.
onClick={e => props.onClick(e, props.id)}
and
toggleAnswer(e, index) {
if (this.state.shownAnswers.indexOf(index) > -1) {
this.setState({
shownAnswers: this.state.shownAnswers.filter(val => val !== index)
});
} else {
this.setState({
shownAnswers: this.state.shownAnswers.concat(index)
});
}
}
Then
When you're passing the class name down to the child component, check if its index is in the "shownAnswers" array to decide which class name to pass.
answerClass={this.state.shownAnswers.indexOf(index) > -1 ? "answer" : "answer-hide"}
Building off your example, it could look something like this (untested):
// RiddlesPage where toggleAnswer function is defined
class RiddlesPage extends Component {
constructor(props) {
super(props);
this.state = {
questionData: [],
shownAnswers: []
};
this.getPageData = this.getPageData.bind(this);
this.toggleAnswer = this.toggleAnswer.bind(this);
}
getPageData() {
console.log("we hit getPageData function starting --");
helpers.getRiddlesPage().then(data => {
console.log("this is the result", data);
this.setState({
questionData: data[0].questionData,
});
});
}
toggleAnswer(e, index) {
if (this.state.shownAnswers.indexOf(index) > -1) {
this.setState({ shownAnswers: this.state.shownAnswers.filter(val => val !== index) });
} else {
this.setState({ shownAnswers: this.state.shownAnswers.concat(index) });
}
}
componentWillMount() {
this.getPageData();
}
render() {
return (
<div>
<Riddles>
{this.state.questionData.map((data, index) => {
return (
<RiddlesItem
key={index}
id={index}
question={data.question}
answer={data.answer}
button={data.buttonURL}
answerClass={this.state.shownAnswers.indexOf(index) > -1 ? "answer" : "answer-hide"}
onClick={this.toggleAnswer}
/>
);
})}
</Riddles>
</div>
);
}
}
export default RiddlesPage;
// Riddles Component
import React from "react";
import "./riddles.css";
const Riddles = props => (
<div id="riddles-row">
<div className="container">
<div className="row">
<div className="col-12">
<div>{props.children}</div>
</div>
</div>
</div>
</div>
);
export default Riddles;
// RiddlesItem Component where onClick function is set as a prop
import React from "react";
import "./riddles.css";
const RiddlesItem = props => (
<div>
<div className="card-body">
<p id="question">{props.question}</p>
<img
className="img-fluid"
id={props.id}
src={props.button}
onClick={e => props.onClick(e, props.id)}
alt="answer button"
/>
<p className={props.answerClass}> {props.answer} </p>
</div>
</div>
);
export default RiddlesItem;

How to filter data in ListView React-native?

I am trying to filter my array object list and then trying to display in the ListView with new DataSource. However, the list is not getting filtered. I know that my filter function works correctly. ( I checked it in the console.log )
I am using Redux to map my state to prop. And then trying to filter the prop. Is this the wrong way?
Here is my code:
/*global fetch:false*/
import _ from 'lodash';
import React, { Component } from 'react';
import { ListView, Text as NText } from 'react-native';
import { connect } from 'react-redux';
import { Actions } from 'react-native-router-flux';
import {
Container, Header, Item,
Icon, Input, ListItem, Text,
Left, Right, Body, Button
} from 'native-base';
import Spinner from '../common/Spinner';
import HealthImage from '../misc/HealthImage';
import { assetsFetch } from '../../actions';
const ds = new ListView.DataSource({
rowHasChanged: (r1, r2) => r1 !== r2
});
class AssetsList extends Component {
componentWillMount() {
this.props.assetsFetch();
// Implementing the datasource for the list View
this.createDataSource(this.props.assets);
}
componentWillReceiveProps(nextProps) {
// Next props is the next set of props that this component will be rendered with.
// this.props is still equal to the old set of props.
this.createDataSource(nextProps.assets);
}
onSearchChange(text) {
const filteredAssets = this.props.assets.filter(
(asset) => {
return asset.name.indexOf(text) !== -1;
}
);
this.dataSource = ds.cloneWithRows(_.values(filteredAssets));
}
createDataSource(assets) {
this.dataSource = ds.cloneWithRows(assets);
}
renderRow(asset) {
return (
<ListItem thumbnail>
<Left>
<HealthImage health={asset.health} />
</Left>
<Body>
<Text>{asset.name}</Text>
<NText style={styles.nText}>
Location: {asset.location} |
Serial: {asset.serial_number}
</NText>
<NText>
Total Samples: {asset.total_samples}
</NText>
</Body>
<Right>
<Button transparent onPress={() => Actions.assetShow()}>
<Text>View</Text>
</Button>
</Right>
</ListItem>
);
}
render() {
return (
<Input
placeholder="Search"
onChangeText={this.onSearchChange.bind(this)}
/>
<ListView
enableEmptySections
dataSource={this.dataSource}
renderRow={this.renderRow}
/>
);
}
}
const mapStateToProps = state => {
return {
assets: _.values(state.assets.asset),
spinner: state.assets.asset_spinner
};
};
export default connect(mapStateToProps, { assetsFetch })(AssetsList);
What am I doing wrong here?

It's a little hard to follow what's going on here. I would simplify it to be like so:
class AssetsList extends Component {
state = {};
componentDidMount() {
return this.props.assetsFetch();
}
onSearchChange(text) {
this.setState({
searchTerm: text
});
}
renderRow(asset) {
return (
<ListItem thumbnail>
<Left>
<HealthImage health={asset.health} />
</Left>
<Body>
<Text>{asset.name}</Text>
<NText style={styles.nText}>
Location: {asset.location} |
Serial: {asset.serial_number}
</NText>
<NText>
Total Samples: {asset.total_samples}
</NText>
</Body>
<Right>
<Button transparent onPress={() => Actions.assetShow()}>
<Text>View</Text>
</Button>
</Right>
</ListItem>
);
}
getFilteredAssets() {
}
render() {
const filteredAssets = this.state.searchTerm
? this.props.assets.filter(asset => {
return asset.name.indexOf(this.state.searchTerm) > -1;
})
: this.props.assets;
const dataSource = ds.cloneWithRows(filteredAssets);
return (
<Input
placeholder="Search"
onChangeText={this.onSearchChange.bind(this)}
/>
<ListView
enableEmptySections
dataSource={dataSource}
renderRow={this.renderRow}
/>
);
}
}
const mapStateToProps = state => {
return {
assets: _.values(state.assets.asset),
spinner: state.assets.asset_spinner
};
};
export default connect(mapStateToProps, { assetsFetch })(AssetsList);
A few points:
Your component is stateful. There is one piece of state that belongs only to the component: the search term. Keep that in component state.
Don't change the data source in life cycle functions. Do it the latest point you know it's needed: in render.
I'm guessing that there's something async in assetFetch, so you probably should return it in componentDidMount.
I changed from componentWillMount to componentDidMount. It's recommended to put async fetching componentDidMount. This can matter if you ever do server side rendering.
Skip filtering if there is no search term. This would only matter if the list is very large.
One thing I have a little concern with is the pattern of fetching inside a component, putting it in global state, and then relying on that component to react to the global state change. Thus changing global state becomes a side effect of simply viewing something. I assume you are doing it because assets is used elsewhere, and this is a convenient point to freshen them from the server so that they will show up in other components that do not fetch them. This pattern can result in hard-to-find bugs.

You need to do setState to trigger render. Here's how I would do it -
constructor(props) {
super(props);
this.ds = new ListView.DataSource({ rowHasChanged: (r1,r2) => r1 !== r2 });
this.state = {
assets: []
};
}
componentWillMount() {
this.props.assetsFetch();
this.setState({
assets: this.props.assets
});
}
componentWillReceiveProps(nextProps) {
this.setState({
assets: nextProps.assets
});
}
onSearchChange(text) {
const filteredAssets = this.props.assets.filter(asset => asset.name.indexOf(text) !== -1);
this.setState({
assets: _.values(filteredAssets)
});
}
render() {
...
<ListView
dataSource={this.ds.cloneWithRows(this.state.assets)}
.....
/>
}